In not a few cases of elements or the like applied to an optical signal processing system and/or an optical communication system, an optical pulse having a rectangular wave shape is assumed as one having an ideal optical waveform to be handled.
For example, an optical element such as a SOA (Semiconductor Optical Amplifier) is driven by an electric signal (driving signal) switched between ON and OFF on a time axis, and is applied as a gate switch for performing switching of conduction/shutoff of input light. As a result of the switching of the driving signal between conduction and shutoff, output light from the SOA becomes an optical pulse that is switched between ON and OFF on a time axis. The optical pulse output from the SOA is often required to have a waveform close to a true (ideal) rectangular wave shape.
Also, some of electronic devices handling binary digital electric signals include an internal element, wiring or the like for which a binary rectangular wave signal is ideal as a signal conducted therethrough. Examples of such electronic devices include transmission line devices such as a memory, a buffer, a modulator, and a high-speed input/output interface device. Also, in such electronic devices, it is often required to allow a signal waveform to be easily shaped into an optimal rectangular shape (see Patent Document 1: Japanese Laid-open Patent Publication No. 9-36471, and Patent Document 2: Japanese Laid-open Patent Publication No. 2000-341728).